Female cats do not normally bleed or have any vaginal discharge during heat. Symptoms of heat may include urine marking, restlessness, calling and behavioral changes. Heat usually lasts for four to six days.
Breeding behavior in cats is triggered by the length of daylight. When the days are longer than 12 hours, mature female cats begin cycling. If not bred, females go into and out of heat every 14 to 21 days throughout the spring. During the summer, the female continues to go into and out of heat, but with longer intervals between heats. Cats are induced ovulators, meaning that the physical act of mating causes them to ovulate. Females who do not mate cycle until the days become shorter than 12 hours.